Abstract Cystic fibrosis (CF) is the most common lethal genetic disorder among Caucasians. As a consequence of mutations in the CFTR gene, most CF patients die from progressive lung disease for which there is no curative treatment. Expression of the CFTR cDNA in as few as 6- 10% of respiratory epithelia can correct the anion transport defect, and therefore gene therapy holds great promise for this autosomal recessive disease. Viral vectors such as adeno- associated virus (AAV) are among the safest tools available to deliver a corrective cargo to the airways, however, inefficient delivery continues to limit the field. We propose to overcome this limitation by using novel peptide epitopes that bind efficiently to the surface of well-differentiaed primary CF airway epithelia from humans and from a novel CF pig model. Our overall hypothesis is that peptide motifs with affinity to the apical surface of CF airway epithelia can be identified via phage panning, and incorporated into an AAV capsid to improve vector tropism for the airways. The newly engineered vectors will be used to correct the CF phenotype by gene addition in well-differentiated epithelia. This collaborative proposal combines expertise in CF and airway epithelial cell biology (Drs. McCray and Zabner) with expertise in phage panning and vector engineering (Drs. Davidson and Zabner). These PIs also have considerable expertise in gene therapy. This proposal encompasses two aims, In Aim 1, we will use panning with a phage display library to identify peptide motifs with affinity to the mucosal surface of well-differentiaed CF airway epithelia. We will test insert those motifs into new AAV capsids that emerged through capsid shuffling strategies and show improved transduction profiles, for improved targeting to the apical surface of CF airway epithelia. In aim 2, we will use the peptide ligand-modified AAVs to correct the CFTR anion transport and host defense defects in CF airway epithelia.